The present invention generally relates to a novel sampling device for sampling blood, or the like. The invention more specifically relates to a novel blood sampling syringe for sampling or drawing blood from a patient which provides significant improvements over the blood sampling syringes of the prior art.
Many techniques and devices have been developed over the years for sampling blood and other bodily fluids from a patient. One such method is utilization of a standard hypodermic syringe. With this method, a hypodermic needle is attached to the syringe, with a piston of the syringe being in a collapsed position. The needle is then inserted through the skin and into a patient's blood vessel. To draw blood from the patient's vascular system, a technician must shift the piston into an extended position, thereby generating a negative pressure within the syringe which, when applied to the vascular system through the needle, draws blood into the syringe. The technician must be careful to shift the piston without removing the needle from the blood vessel while drawing blood in order to avoid injuring the patient.
While effective, this method presents some drawbacks which make it cumbersome to use. For example, to shift the syringe piston into the extended position, the technician often must grasp the syringe with two hands: one hand holding the main body of the syringe while the other shifts the piston.
In an effort to reduce these complications, other devices have been developed. One such device employs a substantially hollow housing upon which a hypodermic needle can be mounted, and a sealed pre-evacuated blood-receiving tube insertable into the housing for operative connection to the needle. In use, the needle is attached to the housing and is inserted into the patient's blood vessel. A portion of the needle extends through the housing and terminates in the hollow interior thereof. A pre-evacuated tube is inserted into the hollow interior such that the terminal end of the needle pierces the seal of the tube. Negative pressure present within the tube is applied through the needle to the patient's blood vessel, thereby drawing blood therefrom into the tube. When the tube is sufficiently full, the tube is removed from the hollow interior, thereby breaking the connection between the needle and the tube, and removing the negative pressure from the blood vessel.
While this device is effective, it also presents drawbacks in some instances which make it incompatible with some patients. Specifically, while the technician need not use both hands to draw blood into the tube, as opposed to the syringe method discussed hereinabove, use of both hands is required when inserting the pre-evacuated tube and removing the filled tube so that the needle will not be dislodged from the blood vessel.
Utilization of the pre-evacuated tube itself can present other problems. Because the tube has been pre-evacuated, the negative pressure applied to the patient is applied rapidly and is not regulated, and the technician lacks control of the rate of blood drawn from the patient's vascular system. For elderly or infant patients who may have delicate or fragile blood vessels, or those who suffer from a vascular disease, their blood vessels may collapse because of the application of unregulated negative pressure, resulting in serious harm to the patient. The pre-evacuated tube also prevents reversal of the blood draw, which may be necessary in some circumstances.
Another improvement in devices for sampling blood is disclosed in the patent to Downey, U.S. Pat. No. 4,813,433, viz. a different construction for a sampling syringe. This syringe generally comprises a hollow tube bifurcated diametrically along an axial length thereof by a partition wall to form two substantially half-cylindrical chambers. A semi- circular piston is shiftably disposed within one chamber which communicates with the other, to which a hypodermic needle is connected, through an aperture in the partition wall. In this manner, as the piston properly shifts within one chamber, a negative pressure is generated in the other chamber, thereby drawing blood into that chamber from the patient.
While this device is also effective, it too presents certain drawbacks. Because this device is also basically a syringe, it has the same two-handed operational requirements and limitations discussed in detail hereinabove. Furthermore, the bifurcated structure of the syringe is cumbersome and expensive to manufacture and difficult to mold from a plastic material. These manufacturing difficulties result in the syringe having an increased cost, thereby reducing the economic disposability thereof. In addition, it is relatively difficult to form and maintain a seal around the semicircular piston required with this design, which further increases the cost of the syringe, as well as making it more complicated to operate.
The novel blood sampling syringe of the present invention is intended to solve some, if not all, of the problems presented by the blood sampling methods and devices of the prior art discussed above. Specifically, the blood sampling syringe of the invention provides for one-handed, controlled negative pressure blood draw from a patient. This syringe allows a technician to gently apply negative pressure to a patient's vascular system. The technician can regulate negative pressure application while also being able to reverse the blood flow in the syringe, if necessary. This novel syringe comprises relatively few parts, is relatively easily and inexpensively molded and manufactured, and is therefore economically disposable.